Load Carrying Efficiency of Floating Ring Journal Bearings

1983 ◽  
Vol 105 (4) ◽  
pp. 605-607 ◽  
Author(s):  
D. F. Wilcock
Keyword(s):  
External Load ◽  
Power Loss ◽  
Full Range ◽  
Journal Bearings ◽  
Length Ratio ◽  
Eccentricity Ratio ◽  
Clearance Ratio ◽  
Isothermal Conditions ◽  
Load Carrying

Floating ring bearings are compared to single film journal bearings over the full range from laminar to turbulent conditions in the films. Isothermal conditions are assumed. Assuming each type carries the same external load and operates at the same eccentricity ratio as determined by the Capacity Number, reductions in the power loss required range from 31 to 64 percent when the clearance ratio C0/(C1 + C2) is held constant and the length is shortened, and from 42 to 63 percent when the length ratio L0/L is held constant and the clearance ratio C0/(C1 + C2) is reduced. Equilibrium ring speeds range from ω0/3 to 0.45 ω0.

Design of Multi-Recess Hydrostatic Journal Bearings for Minimum Total Power Loss

1974 ◽  
Vol 96 (1) ◽  
pp. 226-232 ◽  
Author(s):  
C. Cusano ◽  
T. F. Conry
Keyword(s):  
Rotational Speed ◽  
Power Loss ◽  
Load Capacity ◽  
Maximum Load ◽  
Journal Bearings ◽  
Design Criterion ◽  
Total Power ◽  
Eccentricity Ratio ◽  
Constant Ratio ◽  
Design Charts

The design problem is formulated for multi-recess hydrostatic journal bearings with a design criterion of minimum total power loss. The design is subject to the constraints of constant ratio of the recess area to the total bearing area and maximum load capacity for a given recess geometry. The L/D ratio, eccentricity ratio, ratio of recess area to total bearing area, and shaft rotational speed are considered as parameters. The analysis is based on the bearing model of Raimondi and Boyd [1]. This model is generally valid for low-to-moderate speeds and a ratio of recess area-to-total bearing area of approximately 0.5 or greater. Design charts are presented for bearings having a ratio of recess area-to-total bearing area of 0.6 and employing capillary and orifice restrictors, these being the most common types of compensating elements. A design example is given to illustrate the use of the design charts.

On the Transmissibility of Short Porous Journal Bearings

1978 ◽  
Vol 100 (2) ◽  
pp. 296-302 ◽  
Author(s):  
C. Cusano ◽  
T. F. Conry
Keyword(s):  
Wall Thickness ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Length Ratio ◽  
Rigid Rotor ◽  
Isothermal Conditions

The transmissibility characteristics of oil-lubricated porous journal bearings are analytically determined for a rigid rotor mounted in both the horizontal and the vertical positions. The bearing model used in this investigation is the short-bearing approximation with isothermal conditions and a 180-degree cavitated film. All data presented are for a range of unbalances that may commonly be encountered in practice. These data show that operating conditions exist for which porous journal bearings exhibit transmissibility characteristics that are superior to those of corresponding solid journal bearings. All data presented for porous bearings were obtained by using a bearing with a wall thickness-to-length ratio of 0.2.

Analysis of Noncircular Gas Journal Bearings

1975 ◽  
Vol 97 (4) ◽  
pp. 616-623 ◽  
Author(s):  
O. Pinkus
Keyword(s):  
Reynolds Equation ◽  
Load Capacity ◽  
Full Range ◽  
Maximum Load ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Significant Advance ◽  
Arbitrary Direction ◽  
Isothermal Conditions ◽  
Load Vector

The compressible Reynolds Equation under isothermal conditions was solved for finite elliptical and 3-lobe bearings with the load vector acting in any arbitrary direction over the full range of 360 deg. Envelopes of minimum and maximum eccentricity for a given set of operating conditions are provided, the first to yield maximum load capacity, and the second to assist stability by a choice of the highest possible ε. Some values of the spring and damping forces are also given and it is shown that in comparison with conventional bearings, the non-circular designs offer a significant advance in stiffness, particularly for low ε, when instability is most often encountered.

Theoretical Evaluation of Capacitance, Capacitive Reactance, Resistance and Their Effects on Performance of Hydrodynamic Journal Bearings

1991 ◽  
Vol 113 (4) ◽  
pp. 762-767 ◽  
Author(s):  
H. Prashad
Keyword(s):  
Journal Bearings ◽  
Design Parameters ◽  
Clearance Ratio ◽  
Theoretical Evaluation ◽  
Active Resistance ◽  
Variable Resistor ◽  
Load Carrying ◽  
Capacitive Reactance ◽  
Bearing Design ◽  
Safe Load

A theoretical approach is developed to determine capacitance, capacitive reactance, active resistance, and impedance of hydrodynamic journal bearings under different conditions of operation. It has been established that the bearing capacitance increases with eccentricity and L/D ratios but reduces with increase in clearance ratio. On the contrary, resistance and capacitive reactance of a bearing increase with the clearance ratio but reduce with increase in the eccentricity and L/D ratios. However, the bearing impedance is more affected by the resistance than the capacitive reactance. The bearing behaves like a capacitor till the ratio of capacitive reactance to active resistance is less than unity, and acts like a variable resistor as this ratio exceeds unity. This analysis has a potential to analysis safe load carrying capacity at different speeds of operation by determining the bearing capacitance. Also, this may act as a guide to select the bearing design parameters for safe and reliable operation of a hydrodynamic journal bearing.

Feasibility of Gas-Expanded Lubricants for Increased Energy Efficiency in Tilting-Pad Journal Bearings

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Andres Clarens ◽  
Amir Younan ◽  
Shibo Wang ◽  
Paul Allaire
Keyword(s):  
Supercritical Co2 ◽  
Power Loss ◽  
Load Capacity ◽  
Reducing Power ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Eccentricity Ratio ◽  
Power Losses ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearings

Lubricants are necessary in tilting-pad journal bearings to ensure separation between solid surfaces and to dissipate heat. They are also responsible for much of the undesirable power losses that can occur through a bearing. Here, a novel method to reduce power losses in tilting-pad journal bearings is proposed in which the conventional lubricant is substituted by a binary mixture of synthetic lubricant and dissolved CO2. These gas-expanded lubricants (GELs) would be delivered to a reinforced bearing housing capable of withstanding modest pressures less than 10 MPa. For bearings subject to loads that are both variable and predictable, GELs could be used to adjust lubricant properties in real time. High-pressure lubricants, mostly gases, have already been explored in tilting-pad journal bearings as a means to accommodate higher shaft speeds while reducing power losses and eliminating the potential for thermal degradation of the lubricant. These gas-lubricated bearings have intrinsic limitations in terms of bearing size and load capacity. The proposed system would combine the loading capabilities of conventional lubricated bearings with the efficiency of gas-lubricated bearings. The liquid or supercritical CO2 serves as a low-viscosity and completely miscible additive to the lubricant that can be easily removed by purging the gas after releasing the pressure. In this way, the lubricant can be fully recycled, as in conventional systems, while controlling the lubricant properties dynamically by adding liquid or supercritical CO2. Lubricant properties of interest, such as viscosity, can be easily tuned by controlling the pressure inside the bearing housing. Experimental measurements of viscosity for mixtures of polyalkylene glycol (PAG)+CO2 at various compositions demonstrate that significant reductions in mixture viscosity can be achieved with relatively small additions of CO2. The measured parameters are used in a thermoelastohydrodynamic model of tilting-pad journal bearing performance to evaluate the bearing response to GELs. Model estimates of power loss, eccentricity ratio, and pad temperature suggest that bearings would respond quite favorably over a range of speed and preload conditions. Calculated power loss reductions of 20% are observed when compared with both a reference petroleum lubricant and PAG without CO2. Pad temperature is also maintained without significant increases in eccentricity ratio. Both power loss and pad temperature are directly correlated with PAG-CO2 composition, suggesting that these mixtures could be used as “smart” lubricants responsive to system operating conditions.

Hydrodynamic Lubrication of Journal Bearings with a Polymer Melt

1980 ◽  
Vol 102 (4) ◽  
pp. 858-864
Author(s):  
J. V. Accorsi ◽  
T. A. DeRossett
Keyword(s):  
Power Loss ◽  
Hydrodynamic Lubrication ◽  
Axial Flow ◽  
Polymer Melt ◽  
Pressure Profile ◽  
Journal Bearings ◽  
Test Apparatus ◽  
Eccentricity Ratio ◽  
Newtonian Viscosity ◽  
Rate Relation

An experimental investigation of hydrodynamic lubrication of journal bearings was conducted using a polymer melt as the lubricating fluid. The test apparatus monitored the pressure profile, eccentricity ratio, axial flow rate and frictional power loss for a bearing with L/D = 1.5. Due to the non-Newtonian viscosity/shear-rate relation of the polymer, it was necessary to define a generalized Sommerfeld number in order to plot the data. The results provide a tool for the design of polymer lubricated bearings.

The Effect of Journal Bearing Misalignment on Load and Cavitation for Non-Newtonian Lubricants

1986 ◽  
Vol 108 (4) ◽  
pp. 645-654 ◽  
Author(s):  
R. H. Buckholz ◽  
J. F. Lin
Keyword(s):  
Reynolds Equation ◽  
Numerical Solutions ◽  
Journal Bearings ◽  
Surface Boundary ◽  
Film Rupture ◽  
Aspect Ratios ◽  
Free Surface Boundary Condition ◽  
Load Carrying ◽  
Boundary Location ◽  
Surface Boundary Condition

An analysis for hydrodynamic, non-Newtonian lubrication of misaligned journal bearings is given. The hydrodynamic load-carrying capacity for partial arc journal bearings lubricated by power-law, non-Newtonian fluids is calculated for small valves of the bearing aspect ratios. These results are compared with: numerical solutions to the non-Newtonian modified Reynolds equation, with Ocvirk’s experimental results for misaligned bearings, and with other numerical simulations. The cavitation (i.e., film rupture) boundary location is calculated using the Reynolds’ free-surface, boundary condition.

The Effects of Geometric Irregularities of Journals on the Performance of Porous Bearings

1994 ◽  
Vol 208 (2) ◽  
pp. 141-145 ◽  
Author(s):  
T S Chennabasavan ◽  
R Raman
Keyword(s):  
Theoretical Analysis ◽  
Carrying Capacity ◽  
Load Carrying Capacity ◽  
Eccentricity Ratio ◽  
Attitude Angle ◽  
Load Carrying ◽  
Permeability Variation ◽  
Very High

In the theoretical analysis of porous bearings the journal has so far been assumed to be ideal, that is perfectly cylindrical. In the present analysis the geometric irregularities of the journal, such as circumferential undulations and barrel/bellmouth shapes, are taken into account. The permeability variation along the length of the bearing as found in commercial bearings has also been taken into account. The present analysis reveals that, at the critical Sommerfeld number, the friction is very low compared to the very high value for an ideal journal. The present analysis also reveals that the friction and the attitude angle are lower for any Sommerfeld number and that the load-carrying capacity is lower for any eccentricity ratio than that for an ideal journal.

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